1. Field of the Invention
The present invention relates to a steering system for a marine vessel and, in particular, to a steering system for a marine vessel which has a primary propulsion unit and an auxiliary propulsion unit.
2. Description of the Related Art
Marine vessels are often provided with a primary propulsion unit and an auxiliary propulsion unit. Typically a tie bar couples the primary propulsion unit and the auxiliary propulsion unit. U.S. Pat. No. 6,406,340 to Fetchko et al. and U.S. Pat. No. 7,128,626 to Dudra et al., the full disclosures of which are incorporated herein by reference, both disclose using a tie bar to couple a primary propulsion unit and an auxiliary propulsion unit. This allows the propulsion units to be steered simultaneously.
It is also known to use a cable to couple a primary propulsion unit and an auxiliary propulsion unit. U.S. Pat. No. 4,836,812 to Griffiths, the full disclosure of which is also incorporated herein by reference, discloses using a cable to couple a hydraulic cylinder of a primary propulsion unit to a steering arm of an auxiliary propulsion unit. Coupling the propulsion units with a cable provides the advantage of a flexible and rotatable connecting member. However, connecting the cable to the hydraulic cylinder of the primary propulsion engine may limit rotation of the cable and/or unduly twist the cable when primary propulsion unit is tilted. This may result in jamming and less motion being transmitted to the auxiliary propulsion unit.
There is accordingly a need for an improved steering system for a marine vessel which has a primary propulsion unit and an auxiliary propulsion unit.